163 lines
4.7 KiB
Prolog
Executable File
163 lines
4.7 KiB
Prolog
Executable File
/* $Id: pairs.pl,v 1.1 2008-02-12 17:03:52 vsc Exp $
|
|
|
|
Part of SWI-Prolog
|
|
|
|
Author: Jan Wielemaker
|
|
E-mail: wielemak@science.uva.nl
|
|
WWW: http://www.swi-prolog.org
|
|
Copyright (C): 1985-2006, University of Amsterdam
|
|
|
|
This program is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License
|
|
as published by the Free Software Foundation; either version 2
|
|
of the License, or (at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public
|
|
License along with this library; if not, write to the Free Software
|
|
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
|
|
As a special exception, if you link this library with other files,
|
|
compiled with a Free Software compiler, to produce an executable, this
|
|
library does not by itself cause the resulting executable to be covered
|
|
by the GNU General Public License. This exception does not however
|
|
invalidate any other reasons why the executable file might be covered by
|
|
the GNU General Public License.
|
|
*/
|
|
|
|
:- module(pairs,
|
|
[ pairs_keys_values/3,
|
|
pairs_values/2,
|
|
pairs_keys/2,
|
|
group_pairs_by_key/2,
|
|
transpose_pairs/2,
|
|
map_list_to_pairs/3
|
|
]).
|
|
|
|
/** <module> Operations on key-value lists
|
|
|
|
This module implements common operations on Key-Value lists, also known
|
|
as _Pairs_. Pairs have great practical value, especially due to
|
|
keysort/2 and the library assoc.pl.
|
|
|
|
This library is based on disussion in the SWI-Prolog mailinglist,
|
|
including specifications from Quintus and a library proposal by Richard
|
|
O'Keefe.
|
|
|
|
@see keysort/2, library(assoc)
|
|
@author Jan Wielemaker
|
|
*/
|
|
|
|
%% pairs_keys_values(?Pairs, ?Keys, ?Values) is det.
|
|
%
|
|
% True if Keys holds the keys of Pairs and Values the values.
|
|
%
|
|
% Deterministic if any argument is instantiated to a finite list
|
|
% and the others are either free or finite lists.
|
|
|
|
pairs_keys_values(Pairs, Keys, Values) :-
|
|
( nonvar(Pairs) ->
|
|
pairs_keys_values_(Pairs, Keys, Values)
|
|
; nonvar(Keys) ->
|
|
keys_values_pairs(Keys, Values, Pairs)
|
|
; values_keys_pairs(Values, Keys, Pairs)
|
|
).
|
|
|
|
pairs_keys_values_([], [], []).
|
|
pairs_keys_values_([K-V|Pairs], [K|Keys], [V|Values]) :-
|
|
pairs_keys_values_(Pairs, Keys, Values).
|
|
|
|
keys_values_pairs([], [], []).
|
|
keys_values_pairs([K|Ks], [V|Vs], [K-V|Pairs]) :-
|
|
keys_values_pairs(Ks, Vs, Pairs).
|
|
|
|
values_keys_pairs([], [], []).
|
|
values_keys_pairs([V|Vs], [K|Ks], [K-V|Pairs]) :-
|
|
values_keys_pairs(Vs, Ks, Pairs).
|
|
|
|
%% pairs_values(+Pairs, -Values) is det.
|
|
%
|
|
% Remove the keys from a list of Key-Value pairs. Same as
|
|
% pairs_keys_values(Pairs, _, Values)
|
|
|
|
pairs_values([], []).
|
|
pairs_values([_-V|T0], [V|T]) :-
|
|
pairs_values(T0, T).
|
|
|
|
|
|
%% pairs_keys(+Pairs, -Keys) is det.
|
|
%
|
|
% Remove the values from a list of Key-Value pairs. Same as
|
|
% pairs_keys_values(Pairs, Keys, _)
|
|
|
|
pairs_keys([], []).
|
|
pairs_keys([K-_|T0], [K|T]) :-
|
|
pairs_keys(T0, T).
|
|
|
|
|
|
%% group_pairs_by_key(+Pairs, -Joined:list(Key-Values)) is det.
|
|
%
|
|
% Group values with the same key. For example:
|
|
%
|
|
% ==
|
|
% ?- group_pairs_by_key([a-2, a-1, b-4], X).
|
|
%
|
|
% X = [a-[2,1], b-[4]]
|
|
% ==
|
|
%
|
|
% @param Pairs Key-Value list, sorted to the standard order
|
|
% of terms (as keysort/2 does)
|
|
% @param Joined List of Key-Group, where Group is the
|
|
% list of Values associated with Key.
|
|
|
|
group_pairs_by_key([], []).
|
|
group_pairs_by_key([M-N|T0], [M-[N|TN]|T]) :-
|
|
same_key(M, T0, TN, T1),
|
|
group_pairs_by_key(T1, T).
|
|
|
|
same_key(M, [M-N|T0], [N|TN], T) :- !,
|
|
same_key(M, T0, TN, T).
|
|
same_key(_, L, [], L).
|
|
|
|
|
|
%% transpose_pairs(+Pairs, -Transposed) is det.
|
|
%
|
|
% Swap Key-Value to Value-Key and sort the result on Value
|
|
% (the new key) using keysort/2.
|
|
|
|
transpose_pairs(Pairs, Transposed) :-
|
|
flip_pairs(Pairs, Flipped),
|
|
keysort(Flipped, Transposed).
|
|
|
|
flip_pairs([], []).
|
|
flip_pairs([Key-Val|Pairs], [Val-Key|Flipped]) :-
|
|
flip_pairs(Pairs, Flipped).
|
|
|
|
|
|
%% map_list_to_pairs(:Function, +List, -Keyed)
|
|
%
|
|
% Create a key-value list by mapping each element of List.
|
|
% For example, if we have a list of lists we can create a
|
|
% list of Length-List using
|
|
%
|
|
% ==
|
|
% map_list_to_pairs(length, ListOfLists, Pairs),
|
|
% ==
|
|
|
|
:- module_transparent
|
|
map_list_to_pairs/3,
|
|
map_list_to_pairs2/3.
|
|
|
|
map_list_to_pairs(Function, List, Pairs) :-
|
|
map_list_to_pairs2(List, Function, Pairs).
|
|
|
|
map_list_to_pairs2([], _, []).
|
|
map_list_to_pairs2([H|T0], Pred, [K-H|T]) :-
|
|
call(Pred, H, K),
|
|
map_list_to_pairs2(T0, Pred, T).
|
|
|